An audition clip from Moore's first read for the part alongside her now-co-star, Milo Ventimiglia, showed that sparks flew for the pair from the start.

"Milo and I had to do this chemistry read together," Moore told TODAY's Carson Daly. "We had just met seconds earlier, and then he's nuzzling my neck — which is always comfortable — and we had to pretend like we were about to give birth together."

Rebecca and Jack (aka Mandy Moore and Milo Ventimiglia) go on their first date on the season-three premiere of "This Is Us." Ron Batzdorff/NBC

The rest is Pearson history.

Tune in to NBC Sept. 25 at 9 p.m. ET to see some of that history and more on the season premiere of the time-hopping drama.